The recommended dosage for cod liver oil is usually 1 or 2 teaspoons a day or a corresponding number of capsules. Importantly when you read the nutritional information your cod liver oil dosage should provide at least 1 gram of combined EPA and DHA omega-3 fatty acids.
Cod liver oil has a lot of health benefits to it but it's primarily used as a vitamin D/A supplement. It contains very little essential omega 3 fatty acids.
For a EFA supplement - stick with fish/krill/seal oil